Refrigerating apparatus

ABSTRACT

The capacity of a compressor ( 21 ) in cleaning operation is set based on a Froude number Fr. The Froude number Fr expresses a ratio of an inertial force of a gas refrigerant flowing through a gas side communication pipe ( 70 ) to a gravity working on a liquid in the gas side communication pipe ( 70 ). The capacity of the compressor ( 21 ) in the cleaning operation is set so that the Froude number Fr is larger than 1, whereby the inertial force of the gas refrigerant flowing through the gas side communication pipe ( 70 ) becomes larger than the gravity working on the liquid in the gas side communication pipe ( 70 ) which contains mineral oil and foreign matters. In this connection, the liquid containing the mineral oil and the foreign matters is pushed up by the gas refrigerant even in a perpendicularly extending portion of the gas side communication pipe ( 70 ). Thus, the mineral oil and the foreign matters remaining in the existing liquid side communication pipe ( 60 ) and the existing gas side communication pipe ( 70 ) are recovered.

TECHNICAL FIELD

The present invention relates to a refrigerating apparatus connected toexisting communication pipes for performing cleaning operation of thecommunicating pipes.

BACKGROUND ART

Conventionally, a refrigerating apparatus is known which includes arefrigerant circuit that performs vapor compression refrigeration cycleby circulating a refrigerant. This refrigerating apparatus is composedof indoor and outdoor units connected with each other throughcommunication pipes. The communication pipes are buried inside abuilding in many cases. This causes difficulty in exchanging thecommunication pipes at renewal of the refrigerating apparatus,necessitating introduction of a new refrigerating apparatus using theexisting communication pipes.

Meanwhile, a CFC refrigerant and an HCFC refrigerant, which had beenemployed as a refrigerant filled in a refrigerant circuit until now,have been abolished because they causes adverse influence overenvironment (destruction of the ozone layer and the like). For thisreason, it is required to connect a refrigerating apparatus using an HFCrefrigerant or the like, which is a novel refrigerant, to the existingcommunication pipes that have used the CFC refrigerant or the HCFCrefrigerant. However, the existing communication pipes include residualmineral oil of refrigerating machine oil for the CFC refrigerant or theHCFC refrigerant. Acids and ions generated due to degradation of the CFCrefrigerant, the HCFC refrigerant, and the mineral oil may invitecorrosion of an expansion valve and the like. Therefore, it is necessaryto remove the mineral oil by cleaning the existing communication pipesbefore test run for a newly introduced refrigerating apparatus.

In this connection, a refrigerating apparatus capable of cleaning suchexisting communication pipes has been proposed (for example, see PatentDocument 1). In this refrigerating apparatus, a refrigerant circuit iscomposed in such a fashion that a heat source unit including acompressor and a heat source side heat exchanger is connected to anindoor unit including a user side heat exchanger through first andsecond connection pipes as the existing communication pipes. On thesuction side of the compressor, foreign matter catching means isprovided for separating and recovering mineral oil and foreign mattersfrom a refrigerant. The refrigerating apparatus performs cleaningoperation in a cooling operation mode after an HFC refrigerant is filledto clean the first and second connection pipes by the refrigerantcirculating in the refrigerant circuit, thereby recovering the mineraloil and the foreign matters.

Patent Document 1: Japanese Patent Application Laid Open Publication No.2000-329432A

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

Referring to air conditioners as one type of refrigerating apparatuses,for example, many of them have the outdoor unit and the indoor unitdifferent in height between their installed positions. In such a case, aportion extending in a perpendicular direction is formed in eachcommunication pipe for connecting the outdoor unit and the indoor unit.

For removing the mineral oil and the foreign matters which remain in thecommunication pipes on the gas side, it is necessary to push and flowthe mineral oil and the foreign matters by the flow of a gasrefrigerant. Especially, it is required to push upward the mineral oiland the foreign matters by the gas refrigerant in the perpendicularlyextending portion of the communication pipe on the gas side.

However, the conventional refrigerating apparatuses take less or noconsideration of an operation condition during the cleaning operation.For this reason, the flow rate of the gas refrigerant in thecommunication pipe on the gas side is too low to push and flow themineral oil and the foreign matters in some operation conditions,leaving the mineral oil and the foreign matters in the communicationpipes to cause troubles.

The present invention has been made in view of the above problems andhas its object of obviating troubles in a refrigerating apparatus thatperforms cleaning operation of existing communication pipes by surelyreducing a residual amount of mineral oil and foreign matters in thecommunication pipes.

Means of Solving the Problems

Problem solving means that the present invention provides will bedescribed.

The first and second problem solving means direct to a refrigeratingapparatus which includes a heat source side circuit (11) which isprovided with a compressor (21) and a heat source side heat exchanger(24) and which is connected to a user side heat exchanger (33) by meansof an existing liquid side communication pipe (60) and an existing gasside communication pipe (70), and which performs cleaning operation forremoving refrigerating machine oil for an old refrigerant from theexisting liquid side communication pipe (60) and the existing gas sidecommunication pipe (70) by operating the compressor (21).

In the first problem solving means, an operation condition in thecleaning operation is set based on a Froude number Fr expressed by anexpression Fr=(d_(g)/d_(l))×(U²/gD) where U is a velocity of a gasrefrigerant flowing through the gas side communication pipe (70), D isan inner diameter of the gas side communication pipe (70), d_(g) is adensity of the gas refrigerant flowing through the gas sidecommunication pipe (70), d_(l) is a density of a liquid existing in thegas side communication pipe (70), and g is a gravitational acceleration.

In the second problem solving means, the gas side communication pipe(70) which is connected to the heat source side circuit (11) of therefrigerant apparatus is composed of a plurality of branch pipes (71)respectively connected to a plurality of user side heat exchangers, anda stem pipe (72) to which the plurality of branch pipes (71) areconnected, and an operation condition in the cleaning operation is setbased on a Froude number Fr expressed by an expressionFr=(d_(g)/d_(l))×(U²/gD) where U is a velocity of a gas refrigerantflowing through the stem pipe (72) of the gas side communication pipe(70), D is an inner diameter of the stem pipe (72), d_(g) is a densityof the gas refrigerant flowing through the stem pipe (72), d_(l) is adensity of a liquid existing in the stem pipe (72), and g is agravitational acceleration.

The third and fourth problem solving means direct to a refrigeratingapparatus which includes: a heat source side circuit (11) which isprovided with a compressor (21) and a heat source side heat exchanger(24) and which is connected to a user side heat exchanger (33) by meansof an existing liquid side communication pipe (60) and an existing gasside communication pipe (70); and a recovery container (40) which isprovided on a suction side of the compressor (21) in the heat sourceside circuit (11) and which traps refrigerating machine oil separatedfrom the gas refrigerant, and which performs cleaning operation forrecovering refrigerating machine oil for the old refrigerant remainingin the existing liquid side communication pipe (60) and the existing gasside communication pipe (70) to the recovery container (40) by operatingthe compressor (21).

In the third problem solving means, an operation condition during thecleaning operation is set based on a Froude number Fr expressed by anexpression Fr=(d_(g)/d_(l))×(U²/gD) where U is a velocity of a gasrefrigerant flowing through the gas side communication pipe (70), D isan inner diameter of the gas side communication pipe (70), d_(g) is adensity of the gas refrigerant flowing through the gas sidecommunication pipe (70), d_(l) is a density of a liquid existing in thegas side communication pipe (70), and g is a gravitational acceleration.

In the fourth problem solving means, the gas side communication pipe(70) which is connected to the heat source side circuit (11) of therefrigerant apparatus is composed of a plurality of branch pipes (71)respectively connected to a plurality of user side heat exchangers, anda stem pipe (72) to which the plurality of branch pipes (71) areconnected, and an operation condition in the cleaning operation is setbased on a Froude number Fr expressed by an expressionFr=(d_(g)/d_(l))×(U²/gD) where U is a velocity of a gas refrigerantflowing through the stem pipe (72) of the gas side communication pipe(70), D is an inner diameter of the stem pipe (72), d_(g) is a densityof the gas refrigerant flowing through the stem pipe (72), d_(l) is adensity of a liquid existing in the stem pipe (72), and g is agravitational acceleration.

In the fifth problem solving means, the operation condition in thecleaning operation is set so that the Froude number is larger than 1 inthe first, second, third, or fourth problem solving means,

In the sixth problem solving means, the operation condition in thecleaning operation is set so that the Froude number is 1.5 or larger inthe first, second, third, or fourth problem solving means.

In the seventh problem solving means, the refrigerant filled in the heatsource side circuit (11) is a mixed refrigerant containing R32 or anatural refrigerant in the first, second, third, or fourth problemsolving means.

Operation

In the first and second problem solving means, the heat source sidecircuit (11) is connected to the user side heat exchanger (33) throughthe existing liquid side communication pipe (60) and the existing gasside communication pipe (70). During the cleaning operation for cleaningthe existing liquid side communication pipe (60) and the existing gasside communication pipe (70), the compressor (21) of the heat sourceside circuit (11) is operated to allow the refrigerant to flow throughthe liquid side communication pipe (60) and the gas side communicationpipe (70). During the cleaning operation, also, the refrigeratingmachine oil for the old refrigerant remaining in the existing liquidside communication pipe (60) and the existing gas side communicationpipe (70) is pushed and flown by the refrigerant, thereby being removedfrom the liquid side communication pipe (60) and the gas sidecommunication pipe (70).

In the third and fourth problem solving means, the heat source sidecircuit (11) is connected to the user side heat exchanger (33) throughthe existing liquid side communication pipe (60) and the existing gasside communication pipe (70). During the cleaning operation for cleaningthe existing liquid side communication pipe (60) and the existing gasside communication pipe (70), the compressor (21) of the heat sourceside circuit (11) is operated to allow the refrigerant to flow throughthe liquid side communication pipe (60) and the gas side communicationpipe (70). During the cleaning operation, also, the refrigeratingmachine oil for the old refrigerant remaining in the existing liquidside communication pipe (60) and the existing gas side communicationpipe (70) is flown to the heat source side circuit (11) to be separatedfrom the gas refrigerant, thereby being recovered to the recoverycontainer (40).

In the first and third problem solving means, the Froude number Frexpresses a ratio of an inertial force of the gas refrigerant flowingthrough the gas side communication pipe (70) to a gravity working on theliquid in the gas side communication pipe (70). In other words, theFroude number Fr expresses a magnitude relationship between the gravityworking on the liquid in the gas side communication pipe (70) and theinertial force of the gas refrigerant flowing through the gas sidecommunication pipe (70). These problem solving means set the operationcondition in the cleaning operation based on the Froude number Fr.

Further, in the second and fourth problem solving means, the gas sidecommunication pipe (70) is composed of the plurality of branch pipes(71) and one stem pipe (72). The plurality of branch pipes (71) areconnected at respective one ends thereof to the plurality of user sideheat exchangers (33), respectively, and are connected at the respectiveother ends thereof to the stem pipe (72). The Froude number Fr in theseproblem solving means expresses a ratio of an inertial force of the gasrefrigerant flowing through the stem pipe (72) of the gas sidecommunication pipe (70) to a gravity working on the liquid in the stempipe (72). In other words, the Froude number Fr expresses a magnituderelationship between the gravity working on the liquid in the stem pipe(72) of the gas side communication pipe (70) and the inertial force ofthe gas refrigerant flowing through the stem pipe (72). These problemsolving means set the operation condition in the cleaning operationbased on the Froude number Fr.

Herein, as the liquid that can exists in the gas side communication pipe(70), there are the refrigerating machine oil for the old refrigerant,the new refrigerant, and the refrigerating machine oil for the newrefrigerant. The density d_(l) of the liquid used in introducing theFroude number Fr is preferably a value of the largest density among therefrigerating machine oil for the old refrigerant, the new refrigerant,and the refrigerating machine oil for the new refrigerant. The thus setvale d_(l) is necessarily larger than the density of the mixture of therefrigerating machine oil for the old refrigerant, the new refrigerant,and the refrigerating machine oil for the new refrigerant, so that theliquid in the gas side communication pipe (70) is flown out by the gasrefrigerant surely.

In the fifth problem solving means, the operation condition in thecleaning operation is set so that the Froude number Fr is larger than 1.As described above, the Froude number Fr expresses a ratio of aninertial force of the gas refrigerant flowing through the gas sidecommunication pipe (70) to a gravity working on the liquid in the gasside communication pipe (70). Accordingly, under the condition that theoperation condition is set so that the Froude number Fr is set largerthan 1, the inertial force of the gas refrigerant flowing through thegas side communication pipe (70) becomes larger than the gravity workingon the liquid in the gas side communication pipe (70).

In the sixth problem solving means, the operation condition in thecleaning operation is set so that the Froude number Fr is 1.5 or larger.As described above, the Froude number Fr expresses a ratio of aninertial force of the gas refrigerant flowing through the gas sidecommunication pipe (70) to a gravity working on the liquid in the gasside communication pipe (70). Accordingly, under the condition that theoperation condition is set so that the Froude number Fr is 1.5 orlarger, the inertial force of the gas refrigerant flowing through thegas side communication pipe (70) becomes 1.5 times or further largerthan the gravity working on the liquid in the gas side communicationpipe (70).

In the seventh problem solving means, the mixed refrigerant one ofcomponents of which is R32 or a natural refrigerant is filled in theheat source side circuit (11). As the mixed refrigerant containing R32,HFC mixed refrigerants such as R410A and R407C are exemplified. As thenatural refrigerant, carbon dioxide (CO₂), ammonium (NH₃), hydrocarbonssuch as propane (C₃H₈), and the like are exemplified.

EFFECTS OF THE INVENTION

In the present invention, the operation condition in the cleaningoperation is set based on the Froude number Fr. Specifically, in thefirst and third problem solving means, the operation condition in thecleaning operation is set taking account of the Froude number Frexpressing the relationship between the gravity working on the liquid inthe gas side communication pipe (70) and the inertial force of the gasrefrigerant flowing through the gas side communication pipe (70). Also,in the second and fourth problem solving means, the operation conditionin the cleaning operation is set taking account of the Froude number Frexpressing the relationship between the gravity working on the liquid inthe stem pipe (72) of the gas side communication pipe (70) and therefrigerant flowing through the stem pipe (72).

The old refrigerant and the refrigerating machine oil for the oldrefrigerant are solved in each other to flow into the liquid sidecommunication pipe (60) while foreign matters are flown with theliquid-phase old refrigerant. Thus, the total amount of the refrigerantoil for the old refrigerant and the foreign matters which remain in theliquid side communication pipe (60) becomes very small. Further, theliquid refrigerant flowing through the liquid side communication pipe(60) has a specific gravity larger than that of the gas refrigerantflowing through the gas side communication pipe (70) and the inertialforce of the liquid refrigerant is larger than that of the gasrefrigerant. Accordingly, in the cleaning operation, if therefrigerating machine oil for the old refrigerant and the foreignmatters which remain in the gas side communication pipe (70) can beflown out, the refrigerating machine oil for the old refrigerant and theforeign matters which remain in the liquid side communication pipe (60)can be also flown out.

In view of the above, when the operation condition is set based on theFroude number Fr for the liquid and the gas refrigerant in the gas sidecommunication pipe (70) as in the first and third problem solving means,the refrigerating machine oil for the old refrigerant and the foreignmatters which remain in the liquid side communication pipe (60) and thegas side communication pipe (70) can be flown out by the refrigerantsurely. Further, when the operation condition is set based on the Froudenumber Fr for the liquid and the gas refrigerant in the stem pipe (72)of the gas side communication pipe (70) as in the second and fourthproblem solving means, the refrigerating machine oil for the oldrefrigerant and the foreign matters which remain in the liquid sidecommunication pipe (60) and the gas side communication pipe (70)composed of the stem pipe (72) and the branch pipes (71) can be flownout by the refrigerant surely.

Hence, according to the present invention, the residual amount of therefrigerating machine oil for the old refrigerant and the foreignmatters in the existing communication pipes can be reduced surely by thecleaning operation, obviating troubles caused due to the existence ofthe refrigerating machine oil for the old refrigerant and the foreignmatters.

In the fifth problem solving means, the operation condition in thecleaning operation is set so that the Froude number Fr is larger than 1.Under this condition, the inertial force of the gas refrigerant flowingthrough the gas side communication pipe (70) becomes larger than thegravity working on the liquid in the gas side communication pipe (70),so that the refrigerating machine oil for the old refrigerant and theforeign matters can be pushed upward by the gas refrigerant even at aperpendicularly extending portion of the gas side communication pipe(70). Thus, with this problem solving means, the residual amount of therefrigerating machine oil for the old refrigerant and the foreignmatters in the existing communication pipes can be further reduced.

In the sixth problem solving means, the operation condition in thecleaning operation is set so that the Froude number Fr is 1.5 or larger.Under this condition, the inertial force of the gas refrigerant flowingthrough the gas side communication pipe (70) becomes 1.5 times orfurther larger than the gravity working on the liquid in the gas sidecommunication pipe (70), so that the force of the gas refrigerant forpushing upward the refrigerating machine oil for the old refrigerant andthe foreign matters increases even at the perpendicularly extendingportion of the gas side communication pipe (70). Thus, with this problemsolving means, the residual amount of the refrigerating machine oil forthe old refrigerant and the foreign matters in the existingcommunication pipes can be reduces more surely.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a refrigerant circuit of an air conditioneraccording to Embodiment 1.

FIG. 2 is a graph indicating the relationship between Froude number Frand a residual amount ratio.

FIG. 3 is a diagram showing a refrigerant circuit of an air conditioneraccording to Embodiment 2.

EXPLANATION OF REFERENCE NUMERALS

11 heat source side circuit (outdoor circuit)

21 compressor

24 heat source side heat exchanger (outdoor heat exchanger)

33 user side heat exchanger (indoor heat exchanger)

40 recovery container

60 liquid side communication pipe

70 gas side communication pipe

71 branch pipe

72 stem pipe

BEST MODE FOR CARRYING OUT THE INVENTION

The Embodiments of the present invention will be described in detailwith reference to the drawings.

EMBODIMENT 1

As shown in FIG. 1, an air conditioner of the present embodimentincludes one outdoor unit (20) and one indoor unit (30). The outdoorunit (20) and the indoor unit (30) are constituted for an HFCrefrigerant. The outdoor unit (20) composes a refrigerating apparatusaccording to the present invention.

The outdoor unit (20) and the indoor unit (30) are connected with eachother by means of an existing liquid side communication pipe (60) and anexisting gas side communication pipe (70) which had been respectivelyconnected to an outdoor unit and an indoor unit for a CFC refrigerant oran HCFC refrigerant until then. In the air conditioner of the presentinvention, a refrigerant circuit (10) is formed by connecting an outdoorcircuit (11) of the outdoor unit (20) and an indoor circuit (12) of theindoor unit (30) by means of the existing liquid side communication pipe(60) and the existing gas side communication pipe (70).

The outdoor circuit (11) of the outdoor unit (20) composes a heat sourceside circuit. In the outdoor circuit (11), a compressor (21), an oilseparator (22), a four-way switch valve (23), and an outdoor heatexchanger (24) that serves as a heat source side heat exchanger areconnected by refrigerant piping, which is filled with an HFCrefrigerant. The outdoor unit (20) is provided also with an outdoor fan(24 a).

Referring to the HFC refrigerant filled in the outdoor circuit (11),various refrigerants can be listed such as R32, R134a, R404A, R407C,R410A, R507A, a mixed refrigerant of R32 and R125, a mixed refrigerantof R32, R125, and R134a, and a mixed refrigerant containing R32 as amain component, and the like. Not only the HFC refrigerant but also anatural refrigerant of non-fluorine type may be filled in the outdoorcircuit (11). As the natural refrigerant, CO₂, C_(m)H_(n), NH₃, H₂O, andthe like can be listed.

In the outdoor circuit (11), the discharge side of the compressor (21)is connected to a first port of the four-way switch valve (23) via theoil separator (22). A second port of the four-way switch valve (23) isconnected to one end of the outdoor heat exchanger (24). A third port ofthe four-way switch valve (23) is connected to the suction side of thecompressor (21) via a recovery container (40) described later. A fourthport of the four-way switch valve (23) is connected to a gas sideclosing valve (27). The other end of the outdoor heat exchanger (24) isconnected to a liquid side closing valve (26) through an outdoorexpansion valve (25).

The compressor (21) is a hermetic scroll compressor. Also, thecompressor (21) is of high pressure dome type. In detail, the compressor(21) is so composed that a gas refrigerant compressed in a compressionmechanism (21 b) is once flown in a casing (21 a) and then is flown outfrom the casing (21 a). Refrigerating machine oil for the HFCrefrigerant is trapped at the bottom of the casing (21 a). Synthesizedoil such as Ester oil, ester oil, and the like are used as therefrigerating machine oil.

The compressor (21) is set variable in capacity. Electric power issupplied to a motor (21 c) of the compressor (21) through an inverter(not shown). When the output frequency of the inverter is changed, therotation velocity of the motor (21 c) changes to change the capacity ofthe compressor (21).

The refrigerant circuit (10) is so composed that exchange betweencooling mode operation and heating mode operation is performed byswitching the four-way switch valve (23). Specifically, when a state isswitched to a state that the first port and the second port of thefour-way switch valve (23) communicate with each other while the thirdport and the fourth port communicate with each other (the state shown insolid lines in FIG. 1), the outdoor heat exchanger (24) functions as acondenser while the indoor heat exchanger (33) functions as anevaporator in the refrigerant circuit (10), whereby the refrigerant iscirculated in the cooling mode operation. To the contrary, when thestate is switched to a state that the first port and the fourth port ofthe four-way switch valve (23) communicate with each other while thesecond port and the third port communicate with each other (the stateshown in broken lines in FIG. 1), the outdoor heat exchanger (24)functions as an evaporator while the indoor heat exchanger (33)functions as a condenser in the refrigerant circuit (10), whereby therefrigerant is circulated in the heating mode operation.

The outdoor circuit (11) is provided with the recovery container (40)that recovers foreign matters such as mineral oil of the refrigeratingmachine oil for the old refrigerant remaining in the existing liquidside communication pipe (60) and the existing gas side communicationpipe (70). The recovery container (40) is hermetic and is connected to aflow-in pipe (41) and a flow-out pipe (42). The flow-in pipe (41) isconnected to the third port of the four-way switch valve (23). Theflow-out pipe (42) is connected to the suction side of the compressor(21).

The flow-in pipe (41) is arranged at an outlet end thereof at the bottomin the recovery container (40) so as to open toward the bottom of therecovery container (40). The flow-in pipe (41) is provided with aflow-in valve (51). On the other hand, the flow-out pipe (42) isarranged at an inlet end thereof in the upper part in the recoverycontainer (40) so as to open toward the bottom of the recovery container(40). The flow-out pipe (42) is provided with a flow-out valve (52).Each of the flow-in valve (51) and the flow-out valve (52) composes aswitch valve.

The outdoor circuit (11) is provided with a bypass pipe (54) forbypassing the recovery container (40). The bypass pipe (54) is connectedat one end thereof between the flow-in valve (51) and the third port ofthe four-way switch valve (23) and is connected at the other end thereofbetween the flow-out valve (52) and the suction side of the compressor(21). The bypass pipe (54) is provided with a bypass valve (53) servingas a switch valve.

To the oil separator (22), one end of an oil return pipe (22 a) isconnected. The other end of the oil return pipe (22 a) is connectedbetween the flow-out valve (52) and the suction side of the compressor(21) on further downstream side than a part where the bypass pipe (54)is connected. The synthesized oil discharged from the compressor (21)together with the gas refrigerant is separated from the gas refrigerantby the oil separator (22), and then, is returned to the suction side ofthe compressor (21) through the oil return pipe (22 a).

In the indoor circuit (12) of the indoor unit (30), an indoor expansionvalve (32) and an indoor heat exchanger (33) serving as a user side heatexchanger are connected with each other in series. The indoor unit (30)is provided also with an indoor fan (33 a).

The liquid side communication pipe (60) is connected at one end thereofto the outdoor circuit (11) through a liquid side closing valve (26).The other end of the liquid side communication pipe (60) is connected tothe indoor circuit (12) of the indoor unit (30) by means of a liquidside connector (31). Further, the gas side communication pipe (70) isconnected at one end thereof to the outdoor circuit (11) through a gasside closing valve (27). The other end of the gas side communicationpipe (70) is connected to the indoor circuit (12) of the indoor unit(30) by means of a gas side connector (34)

In the air conditioner of the present embodiment, the capacity of thecompressor (21) in the cleaning operation is set based on Froude numberFr expressed by the following expression.Fr=(d _(g) /d _(l))×(U ² /gD)  (Expression 1)

In the above expression, the Froude number Fr is a dimensionless numberexpressing a ratio of an inertial force of the gas refrigerant flowingthrough the gas side communication pipe (70) to a gravity working on aliquid in the gas side communication pipe (70). In the expression, U isa velocity of the gas refrigerant flowing thought the gas sidecommunication pipe (70) and its unit is [m/s]. D is an inner diameter ofthe gas side communication pipe (70) and its unit is [m]. d_(g) is adensity of the gas refrigerant flowing through the gas sidecommunication pipe (70) and its unit is [kg/m³]. d_(l) is a density ofthe liquid existing in the gas side communication pipe (70) and its unitis [kg/m³]. g is a gravitational acceleration and its unit is [m/s²].

During the cleaning operation, mineral oil (the refrigerating machineoil for the old refrigerant), the new refrigerant, the synthesized oil(the refrigerating machine oil for the new refrigerant), and solid-stateor liquid-state foreign matters exist in the gas side communication pipe(70) in a mixed state. The solid-state or liquid-state foreign mattersinclude detrital powder generated due to sliding of the compressor (21),various kinds of acids and ions generated due to degradation of themineral oil and the old refrigerant, and moisture that has beenpenetrated in the piping. The mixture of the mineral oil, the newrefrigerant, the synthesized oil, and the various kinds of foreignmatters are pushed and flown by the gas refrigerant during the cleaningoperation.

Wherein, it is difficult or impossible to estimate and measure each rateof the components of the mixture existing in the gas side communicationpipe (70). Further, each rate of the components of the mixture variesmoment to moment during the cleaning operation. Under the circumstances,it is desirable to use the largest value that can be estimated as thedensity d_(l) of the liquid existing in the gas side communication pipe(70).

Specifically, the liquid that can exist in the gas side communicationpipe (70) are the mineral oil, the new refrigerant, and the synthesizedoil. In view that the amount of the foreign matters such as detritalpowder is not so large, the largest density value among the mineral oil,the new refrigerant, and the synthesized oil is desirably used as avalue of the density d_(l) of the liquid used in introducing the Froudenumber Fr. For example, when R410A is used as the new refrigerant, thedensity of R410A in a liquid state is the largest of the three.Accordingly, it is desirable to use the density of the liquid-stateR410A as the value of the density d_(l) of the liquid in this case.

In the cleaning operation, the Froude number Fr may be set based onopenings of the outdoor expansion valve (32) and the indoor expansionvalve (25) which are provided in the refrigerant circuit (10) or flowrates of the outdoor fan (24 a) and the indoor fan (33 a) which areprovided in the refrigerant circuit (10). When the openings of theexpansion valves (25, 32) or the flow rates of the fans (24 a, 33 a) aredetermined, a refrigerant circulation rate in the refrigerant circuit(10) is determined to determine the velocity of the gas refrigerantflowing through the gas side communication pipe (70).

Method for Replacing Indoor and Outdoor Units

In renewal of an air conditioner using the CFC refrigerant or the HCFCrefrigerant as the old refrigerant, the existing liquid sidecommunication pipe (60) and the existing gas side communication pipe(70) are used as they are and the existing outdoor unit and the existingindoor unit are replaced to the new outdoor unit (20) and the new indoorunit (30) for the HFC refrigerant as the new refrigerant.

Specifically, the CFC refrigerant or the HCFC refrigerant is recoveredfrom the air conditioner first. Then, the existing outdoor unit and theexisting indoor unit for the CFC refrigerant or the HCFC refrigerant areremoved from the existing liquid side communication pipe (60) and theexisting gas side communication pipe (70). Subsequently, the outdoorunit (20) and the indoor unit (30) for the HFC refrigerant are connectedto the existing liquid side communication pipe (60) and the gas sidecommunication pipe (70) by means of the connectors (31, 34) withintervention of the closing valves (26, 27) to form the aforementionedrefrigerant circuit (10).

Next, under the condition that the liquid side closing valve (26) andthe gas side closing valve (27) are closed, the indoor unit (30), theliquid side communication pipe (60), and the gas side communication pipe(70) are vacuumed to remove air, moisture, and the like in therefrigerant circuit (10) except the outdoor unit (20). Then, the liquidside closing valve (26) and the gas side closing valve (27) are opened,and the HFC refrigerant is added and filled in the refrigerant circuit(10).

Cleaning Operation

The cleaning operation of the aforementioned air conditioner will bedescribed next. The cleaning operation is performed for removing foreignmatters such as mineral oil remaining in the existing liquid sidecommunication pipe (60) and the existing gas side communication pipe(70), and is performed immediately after installation of the indoor unit(30) an the outdoor unit (20) for the HFC refrigerant.

After installation of the indoor unit (30) and the outdoor unit (20) forthe HFC refrigerant, the compressor (21) is started operating and thefour-way switch valve (23) is switched to the state indicated by thesolid lines in FIG. 1. Further, the flow-in valve (51) and the flow-outvalve (52) are opened while the bypass valve (53) is closed. Wherein,during the cleaning operation, each opening of the outdoor expansionvalve (25) and the indoor expansion valve (32) is adjustedappropriately.

When the compressor (21) is operated, the compressed gas refrigerant isdischarged from the compressor (21). The thus discharged gas refrigerantflows to the four-way switch valve (23) via the oil separator (22). Thegas refrigerant after passing through the four-way switch valve (23)flows into the outdoor heat exchanger (24) to be heat-exchanged withoutdoor air, thereby being condense. Then, the condensed liquidrefrigerant passes through the outdoor expansion valve (25) and flowsinto the liquid side communicating pipe (60) through the liquid sideclosing valve (26).

In the liquid side communication pipe (60), the mineral oil of therefrigerating machine oil for the old refrigerant and the foreignmatters remain. The mineral oil and the foreign matters are pushed andflown by the liquid refrigerant flowing in the liquid side communicationpipe (60). Then, the mixture of the liquid refrigerant and a liquidcontaining the mineral oil and the foreign matters flows into the indoorheat exchanger (33) through the indoor expansion valve (32). In theindoor heat exchanger (33), the liquid refrigerant is heat-exchangedwith indoor air to be evaporated. The evaporated refrigerant flows intothe gas side communication pipe (70) together with the liquid containingthe mineral oil and the foreign matters.

In the gas side communication pipe (70), the mineral oil of therefrigerating machine oil for the old refrigerant and the foreignmatters remain. The mineral oil and the foreign matters are pushed andflown by the gas refrigerant together with the liquid containing themineral oil and the foreign matters flown from the liquid sidecommunication pipe (60). Then, the mixture of the gas refrigerant andthe liquid containing the mineral oil and the foreign matters passesthrough the gas side closing valve (27) and the four-way switch valve(23) to flow into the recovery container (40) through the flow-in pipe(41).

The mixture of the gas refrigerant and the liquid containing the mineraloil and the foreign matters which has flown in the recovery container(40) is discharged toward the bottom of the recovery container (40). Theliquid containing the mineral oil and the foreign matters out of themixture is trapped at the bottom of the recovery container (40). The gasrefrigerant flows out from the recovery container (40) to therefrigerant circuit (10) through the flow-out pipe (42), and then, flowsinto the compressor (21) from the suction side of the compressor (21).

The aforementioned cleaning operation for a predetermine time periodcauses the liquid containing the mineral oil and the foreign matters andremaining in the existing liquid side communication pipe (60) and theexisting gas side communication pipe (70) to be recovered into therecovery container (40) together with the gas refrigerant flowing in therefrigerant circuit (10), thereby removing the mineral oil of therefrigerating machine oil for the old refrigerant and the foreignmatters from the liquid side communication pipe (60) and the gas sidecommunication pipe (70).

After the cleaning operation, the flow-in valve (51) and the flow-outvalve (51) are closed and the bypass valve (53) is closed. Thereafter,the flow-in valve (51) and the flow-out valve (52) are closed all thetime while the bypass valve (53) is opened all the time. Under thiscondition, normal operation is exchanged between the cooling modeoperation and the heating mode operation.

Cooling Mode Operation and Heating Mode Operation

In the cooling mode operation, the four-way switch valve (23) is in thestate shown as the solid lines in FIG. 1. The refrigerant dischargedfrom the compressor (21) flows into the oil separator (22), passesthrough the four-way switch valve (23), and then, is heat-exchanged withoutdoor air by the outdoor heat exchanger (24) to be condensed. Thecondensed refrigerant passes through the outdoor expansion valve (25),flows through the liquid side communication pipe (60), and then, isheat-exchanged with indoor air by the indoor heat exchanger (33) to beevaporated. The evaporated refrigerant flows through the gas sidecommunication pipe (70) and passes through the four-way switch valve(23) and the bypass pipe (54) to be returned to the suction side of thecompressor (21).

On the other hand, in the heating mode operation, the four-way switchvalve (23) is in the state shown as the broken lines in FIG. 1. Therefrigerant discharged from the compressor (21) flows into the oilseparator (22), passes through the four-way switch valve (23) and thegas side communication pipe (70), and then, is heat-exchanged withindoor air by the indoor heat exchanger (33) to be condensed. Thecondensed refrigerant flows through the liquid side communication pipe(60), passes through the outdoor expansion valve (25), and then, isheat-exchanged with outdoor air by the outdoor heat exchanger (24) to beevaporated. The evaporated refrigerant passes through the four-wayswitch valve (23) and the bypass pipe (54) to be returned to the suctionside of the compressor (21).

Operation Condition in Cleaning Operation

As described above, during the cleaning operation of the aforementionedair conditioner, the liquid containing the mineral oil and the foreignmatters and remaining in the existing liquid side communication pipe(60) and the existing gas side communication pipe (70) is pushed andflown by the refrigerant flowing in the refrigerant circuit (10) to berecovered in the recovery container (40). It is noted that during thecleaning operation, it is possible to perform dry operation in which therefrigerant flowing through the gas side communication pipe (70) is in avapor phase only or to perform wet operation in which the refrigerantflowing in the gas side communication pipe (70) is in two phases ofvapor and liquid.

In the aforementioned air conditioner, the outdoor unit (20) is arrangedat an upper level than the indoor unit (30). In this case, the liquidside communication pipe (60) and the gas side communication pipe (70)are arranged in a perpendicular direction. In the cleaning operation ofthe thus arranged air conditioner, the liquid refrigerant flows downwardthrough the liquid side communication pipe (60) while the gasrefrigerant flows upward through the gas side communication pipe (70).

In the air conditioner according to the present embodiment, the capacityof the compressor (21) in the cleaning operation is set so that theFroude number Fr is larger than 1. Under the condition, the inertialforce of the gas refrigerant flowing through the gas side communicationpipe (70) is larger than the gravity working on the liquid containingthe mineral oil and the foreign matters and remaining in the gas sidecommunication pipe (70). In other words, the resultant force affectingon the liquid containing the mineral oil and the foreign matters becomesupward in the perpendicularly extending portion of the gas sidecommunication pipe (70). Accordingly, the liquid containing the mineraloil and the foreign matters is pushed up by the gas refrigerant even inthe perpendicularly extending portion of the gas side communication pipe(70). In this way, the liquid containing the mineral oil and the foreignmatters and remaining in the existing gas side communication pipe (70)is removed from the existing gas side communication pipe (70) by thecleaning operation. Then, the liquid containing the mineral oil and theforeign matters removed from the existing gas side communication pipe(70) is recovered surely to the recovery container (40).

The old refrigerant and the mineral oil of the refrigerating machine oilfor the old refrigerant are solved in each other to flow through theliquid side communication pipe (60) while the foreign matters are flownwith the liquid-phase old refrigerant. Therefore, the amount of themineral oil and the foreign matters which remain in the liquid sidecommunication pipe (60) is very small. Further, the liquid refrigerantflows downward through the liquid side communication pipe (60) duringthe cleaning operation. Accordingly, the mineral oil and the foreignmatters remaining in the liquid side communication pipe (60) is pushedand flown downward by the liquid refrigerant. Under the circumstances,when the Froude number Fr in the gas side communication pipe (70) istaken into consideration, the mineral oil and the foreign matters can beremoved surely also from the liquid side communication pipe (60).

In the air conditioner according to the present embodiment, the capacityof the compressor (21) in the cleaning operation is set so that theFroude number Fr in the gas side communication pipe (70) is largerthan 1. The reason why it is so set will be described with reference toFIG. 2.

In FIG. 2, the axis of abscissas indicates the Froude number Frexpressed by Expression 1 while the axis of ordinates indicates aresidual amount ratio. The residual amount ratio means a ratio of anamount of the mineral oil and the foreign matters which remain in theliquid side communication pipe (60) and the gas side communication pipe(70) after one- to three-hour cleaning operation to a standard value,wherein the standard value is a tolerable amount of the mineral oil andthe foreign matters which remain in the liquid side communication pipe(60) and the gas side communication pipe (70).

As shown in FIG. 2, the residual amount ratio decreases as the Froudenumber Fr becomes larger in the range where the Froude number is largerthan 1. Because, the difference between the inertial force of the gasrefrigerant and the gravity working on the liquid containing the mineraloil and the foreign matters becomes larger as the Froude number Frbecomes larger, so that the force that the liquid containing the mineraloil and the foreign matters receives from the gas refrigerant increases.Further, the gradient of the residual amount ratio to the Froude numberFr becomes further larger in the range where the Froude number Fr is 1.4or larger, and the residual amount ratio becomes 1 or smaller in therange where the Froude number Fr is 1.5 or larger. Furthermore, theresidual amount ratio becomes about 0.3 at the point where the Froudenumber Fr is 1.6, and the residual amount ratio decreases very gently inthe range where the Froude number is 1.6 or larger.

In this way, in the range where the Froude number is in the rangebetween 1 and 1.5, the residual amount ratio after performing thecleaning operation for one to three hours becomes larger than 1. Inother words, after the cleaning operation, a larger amount of themineral oil and the foreign matters than the tolerable amount remain inthe liquid side communication pipe (60) and the gas side communicationpipe (70). However, if the cleaning operation is performed furtherlonger, the residual amount ratio can be reduced to 1 or smaller,achieving reduction of the amount of the mineral oil and the foreignmatters which remain in the liquid side communication pipe (60) and thegas side communication pipe (70) to an amount less than the tolerableamount.

In view of the above, the capacity of the compressor (21) is set so thatthe Froude number Fr is smaller than 1. Further, it is desirable to setthe capacity of the compressor (21) so that the Froude number Fr is 1.5or larger, and it is the most desirable to set it so that the Froudenumber Fr is about 1.6.

Wherein, in the aforementioned cleaning operation, the capacity of thecompressor (21) is set so that the upper limit of the Froude number Fris 120. Also, under the condition that the capacity of the compressor(21) is set so that the Froude number Fr is 1.5 or larger, the cleaningoperation for the existing liquid side communication pipe (60) and theexisting gas side communicating pipe (70) to reduce the residual amountratio to 1 or smaller can be completed within only one to three hourseven in the case where operation conditions such as an outdoor aircondition and the like are different.

Wherein, the capacity of the compressor (21) in the cleaning operationis set beforehand in the step of designing the air conditioner so thatthe Froude number Fr is larger than 1 even under the severest conditionthat is assumable. The severest condition is an operation condition thatthe density d_(g) of the gas refrigerant in the gas side communicationpipe (70) is the smallest while the density d_(l) of the liquidrefrigerant in the gas side communication pipe (70) is the largest amongassumable operation conditions. Further, as a value of the density d_(l)of the liquid refrigerant, the largest value of the densities of theliquid components that can exist in the gas side communication pipe (70)is used. The thus set value of the density d_(l) necessarily becomeslarger than the density of the liquid refrigerant existing in the gasside communication pipe (70). When the compressor (21) with the capacityin the cleaning operation so set as above is operated, the Froude numberFr in the gas side communication pipe (70) surely becomes larger than 1so that the liquid refrigerant in the gas side communication pipe (70)is pushed and flown by the gas refrigerant surely.

Wherein, the values of the density d_(g) of the gas refrigerant and thedensity d_(l) of the liquid refrigerant vary depending on temperatureand pressure. In this viewpoint, the air conditioner according to thepresent embodiment corrects the predetermined set value of the capacityof the compressor (21) in the cleaning operation, taking account ofactually measured values and estimated values of temperature andpressure at the time when the actual cleaning operation is performed.

It is noted that it is possible that the capacity of the compressor (21)which is suitable for the cleaning operation is stored for each ofplural operation conditions and a capacity suitable for an operationcondition at the actual cleaning operation is selected among theplurality of stored set values. In this case, tests under variousoperation conditions are performed in the step of designing the airconditioner to determine the capacity of the compressor (21) whichenables sure cleaning of the gas side communication pipe (70) by thecleaning operation under each operation condition and the determinedvalues are stored in the air conditioner.

Effects of Embodiment 1

In the present embodiment, the capacity of the compressor (21) in thecleaning operation is set based on the Froude number Fr. In detail, thecapacity of the compressor (21) in the cleaning operation is set takingaccount of the Froude number Fr that expresses the relationship betweenthe gravity working on the liquid in the gas side communication pipe(70) and the inertial force of the gas refrigerant flowing through thegas side communication pipe (70).

The old refrigerant and the mineral oil of the refrigerating machine oilfor the old refrigerant are solved in each other to flow through theliquid side communication pipe (60) while the foreign matters are flownwith the liquid-phase old refrigerant. Therefore, the amount of themineral oil and the foreign matters which remain in the liquid sidecommunication pipe (60) is very small. The liquid refrigerant flowingthrough the liquid side communication pipe (60) has a specific gravitylarger than the gas refrigerant flowing through the gas sidecommunication pipe (70) and the inertial force of the liquid refrigerantis larger than the inertial force of the gas refrigerant. Accordingly,if the mineral oil and the foreign matters which remain in the gas sidecommunication pipe (70) can be pushed and flown, the mineral oil and theforeign matters which remain in the liquid side communication pipe (60)can be also pushed and flown.

Accordingly, when the capacity of the compressor (21) is set based onthe Froude number Fr relating to the liquid and the gas refrigerant inthe gas side communication pipe (70), the liquid containing the mineraloil and the foreign matters and remaining in the liquid sidecommunication pipe (60) and the gas side communication pipe (70) can bepushed and flown by the refrigerant to be recovered to the recoverycontainer (40). Hence, according to the present embodiment, the residualamount of the mineral oil and the foreign matters which remain in theexisting liquid side communication pipe (60) and the existing gas sidecommunication pipe (70) can be reduced surely by the cleaning operation,obviating troubles caused due to the existence of the mineral oil.

In the present embodiment, also, the capacity of the compressor (21) inthe cleaning operation is set so that the Froude number Fr is largerthan 1. Under this condition, the inertial force of the gas refrigerantflowing through the gas side communication pipe (70) becomes larger thanthe gravity working on the liquid containing the mineral oil and theforeign matters and remaining in the gas side communication pipe (70) tocause the gas refrigerant to push upward the liquid containing themineral oil and the foreign matters even in the perpendicularlyextending portion of the gas side communication pipe (70). Hence,according to the present embodiment, the residual amount of the mineraloil and the foreign matters in the existing liquid side communicationpipe (60) and the existing gas side communication pipe (70) can bereduced further.

Moreover, when the capacity of the compressor (21) in the cleaningoperation is set so that the Froude number Fr is 1.5 or lager, theinertial force of the gas refrigerant flowing through the gas sidecommunication pipe (70) is 1.5 times or further larger than the gravityworking on the liquid containing the mineral oil and the foreign mattersand remaining in the gas side communication pipe (70) so that the forceof the gas refrigerant for pushing the liquid containing the mineral oiland the foreign matters upward increases even at the perpendicularlyextending portion of the gas side communication pipe (70). Therefore,one- to three-hour cleaning operation can surely reduce the residualamount of the mineral oil and the foreign matters in the existing liquidside communication pipe (60) and the existing gas side communicationpipe (70).

Modified Example of Embodiment 1

In Embodiment 1, one compressor (21) is provided and the outputfrequency of the inverter is adjusted to set the capacity of thecompressor (21). Beside the above, it is possible that a plurality ofcompressors (21) are provided and the number of compressors (21) underoperation is changed to set the capacity of the compressors (21).

Embodiment 2

Embodiment 2 of the present invention will be described. In the presentembodiment, the constitution of the air conditioner in Embodiment 1 ischanged. Herein, the subject matter of the present embodiment differentfrom Embodiment 1 will be described.

In Embodiment 2 of the present embodiment, the constitution of the airconditioner in Embodiment 1 is changed. Herein, the subject matter ofthe present embodiment different from Embodiment 1 will be described.

The air conditioner in the present embodiment includes one outdoor unit(20) and three indoor unit (30, 30, 30). Wherein, the number of theindoor units (30) is a mere example. An indoor circuit (12) is providedin each of the indoor units (30). An outdoor circuit (11) of the outdoorunit (20) and each indoor circuit (12) of the indoor units (30) areconnected with each other by means of the existing liquid sidecommunication pipe (60) and a gas side communication pipe (70) tocompose a refrigerant circuit (10).

In each indoor circuit (12) of the indoor units (12), an indoorexpansion valve (32) and an indoor heat exchanger (33) are connectedwith each other in series. Each indoor unit (30) is provided with anindoor fan (33 a).

The liquid side communication pipe (60) is composed of one stem pipe(62) and three branch pipes (61, 61, 61). The stem pipe (62) of theliquid side communication pipe (60) is connected at one end thereof tothe outdoor circuit (11) through a liquid side closing valve (26). Also,the stem pipe (62) of the liquid side communication pipe (60) isconnected to the three branch pipes (61, 61, 61). The branch pipes (61,61, 61) of the liquid side communication pipe (60) are connected to theindoor circuits (12) of the indoor units (30) by means of liquid sideconnectors (31), respectively.

The aforementioned gas side communicating pipe (70) is composed of onestem pipe (72) and three branch pipes (71, 71, 71). The stem pipe (72)of the gas side communication pipe (70) is connected at one end thereofto the outdoor circuit (11) through a gas side closing valve (26). Also,the stem pipe (72) of the gas side communication pipe (70) is connectedto the three branch pipes (71, 71, 71). The branch pipes (71, 71, 71) ofthe gas side communication pipe (70) are connected to the indoorcircuits (12) of the indoor units (30) by means of gas side connectors(34), respectively.

In the air conditioner according to the present embodiment, the capacityof the compressor (21) in the cleaning operation is set based on theFroude number Fr expressed by Expression 1, likewise Embodiment 1.Wherein, the definition of U, D, d_(g), and d_(l) in the presentembodiment is different from that in Embodiment 1. Specifically, U is avelocity of the gas refrigerant flowing through the stem pipe (72) ofthe gas side communication pipe (70). D is an inner diameter of the stempipe (72) of the gas side communication pipe (70). d_(g) is a density ofthe gas refrigerant flowing through the stem pipe (72) of the gas sidecommunication pipe (70). d_(l) is a density of the liquid existing inthe stem pipe (72) of the gas side communication pipe (70).

In the case, for example, where the outdoor unit (20) is arranged on aroof of a building while the indoor units (30) are arranged onrespective floors inside the building, it is general that the branchpipes (71, 71, 71) of the gas side communication pipe (70) are arrangedalong the respective ceilings horizontally while the stem pipe (72)thereof is arranged in the perpendicular direction. With sucharrangement, the mineral oil and the foreign matters can be removedsurely from the branch pipes (71, 71, 71) by taking account of theFroude number Fr in the stem pipe (72) of the gas side communicationpipe (70).

In the air conditioner according to the present embodiment, the capacityof the compressor (21) in the cleaning operation is set so that theFroude number is larger than 1. Under this condition, the inertial forceof the gas refrigerant flowing through the stem pipe (72) becomes largerthan the gravity working on the liquid containing the mineral oil andthe foreign matters and remaining in the stem pipe (72) of the gas sidecommunication pipe (70). In other words, the resultant force affectingon the liquid containing the mineral oil and the foreign matters becomesupward in the stem pipe (72) of the gas side communication pipe (70). Inthis connection, the liquid containing the mineral oil and the foreignmatters is pushed up by the gas refrigerant even in the perpendicularlyextending stem pipe (72) of the gas side communication pipe (70). Inthis way, the liquid containing the mineral oil and the foreign mattersand remaining in the existing gas side communication pipe (70) isremoved from the existing gas side communication pipe (70) by thecleaning operation. Then, the liquid containing the mineral oil and theforeign matters which has been removed from the existing gas sidecommunication pipe (70) is recovered to the recovery container (40)surely.

It is noted that the capacity of the compressor (21) may be set so thatthe Froude number Fr is larger than 1 in both the stem pipe (72) and thebranch pipes (71, 71, 71) of the gas side communication pipe (70).

In the present embodiment, the capacity of the compressor (21) in thecleaning operation is set taking account of the Froude number Fr thatexpresses the relationship between the gravity working on the liquid inthe gas side communication pipe (70) and the gas refrigerant flowingthrough the stem pipe (72) thereof.

As described above, if the mineral oil and the foreign matters whichremain in the gas side communication pipe (70) can be flown out, themineral oil and the foreign matters which remain in the liquid sidecommunication pipe (60) can be flown out, also. Accordingly, when thecapacity of the compressor (21) is set based on the Froude number Frrelating to the liquid and the gas refrigerant in the stem pipe (72) ofthe gas side communication pipe (70), the liquid containing the mineraloil and the foreign matters and remaining in the liquid sidecommunication pipe (60) and the stem pipe (72) and the branch pipes (71,71, 71) of the gas side communication pipe (70) can be pushed and flownby the refrigerant surely to be recovered into the recovery container(40). Hence, according to the present embodiment, the residual amount ofthe mineral oil and the foreign matters in the existing liquid sidecommunication pipe (60) and the existing gas side communication pipe(70) can be reduced surely by the cleaning operation even in the casewhere the plurality of indoor heat exchangers (33) are connected to therefrigerating apparatus, obviating troubles caused due to the existenceof the mineral oil.

INDUSTRIAL APPLICABILITY

As described above, the present invention relates to a refrigeratingapparatus connected to existing communication pipes and is useful forperforming cleaning operation of the communication pipes.

1. A refrigerating apparatus comprising: a heat source side circuit (11)which is provided with a compressor (21) and a heat source side heatexchanger (24) and which is connected to a user side heat exchanger (33)by means of an existing liquid side communication pipe (60) and anexisting gas side communication pipe (70), the refrigerating apparatusperforming cleaning operation for removing refrigerating machine oil foran old refrigerant from the existing liquid side communication pipe (60)and the existing gas side communication pipe (70) by operating thecompressor (21), wherein an operation condition in the cleaningoperation is set based on a Froude number Fr expressed by an expressionFr=(d_(g)/d_(l))×(U²/gD) where U is a velocity of a gas refrigerantflowing through the gas side communication pipe (70), D is an innerdiameter of the gas side communication pipe (70), d_(g) is a density ofthe gas refrigerant flowing through the gas side communication pipe(70), d_(l) is a density of a liquid existing in the gas sidecommunication pipe (70), and g is a gravitational acceleration.
 2. Arefrigerating apparatus comprising: a heat source side circuit (11)which is provided with a compressor (21) and a heat source side heatexchanger (24) and which is connected to user side heat exchangers (33)by means of an existing liquid side communication pipe (60) and anexisting gas side communication pipe (70), the refrigerating apparatusperforming cleaning operation for removing refrigerating machine oil foran old refrigerant from the existing liquid side communication pipe (60)and the existing gas side communication pipe (70) by operating thecompressor (21), wherein the gas side communication pipe (70) which isconnected to the heat source side circuit (11) of the refrigerantapparatus is composed of a plurality of branch pipes (71) respectivelyconnected to the plurality of user side heat exchangers, and a stem pipe(72) to which the plurality of branch pipes (71) are connected, and anoperation condition in the cleaning operation is set based on a Froudenumber Fr expressed by an expression Fr=(d_(g)/d_(l))×(U²/gD) where U isa velocity of a gas refrigerant flowing through the stem pipe (72) ofthe gas side communication pipe (70), D is an inner diameter of the stempipe (72), d_(g) is a density of the gas refrigerant flowing through thestem pipe (72), d_(l) is a density of a liquid existing in the stem pipe(72), and g is a gravitational acceleration.
 3. A refrigeratingapparatus comprising: a heat source side circuit (11) which is providedwith a compressor (21) and a heat source side heat exchanger (24) andwhich is connected to a user side heat exchanger (33) by means of anexisting liquid side communication pipe (60) and an existing gas sidecommunication pipe (70); and a recovery container (40) which is providedon a suction side of the compressor (21) in the heat source side circuit(11) and which traps refrigerating machine oil separated from the gasrefrigerant, the refrigerating apparatus performing cleaning operationfor recovering refrigerating machine oil for the old refrigerantremaining in the existing liquid side communication pipe (60) and theexisting gas side communication pipe (70) to the recovery container (40)by operating the compressor (21), wherein an operation condition duringthe cleaning operation is set based on a Froude number Fr expressed byan expression Fr=(d_(g)/d_(l))×(U²/gD) where U is a velocity of a gasrefrigerant flowing through the gas side communication pipe (70), D isan inner diameter of the gas side communication pipe (70), d_(g) is adensity of the gas refrigerant flowing through the gas sidecommunication pipe (70), d_(l) is a density of a liquid existing in thegas side communication pipe (70), and g is a gravitational acceleration.4. A refrigerating apparatus comprising: a heat source side circuit (11)which is provided with a compressor (21) and a heat source side heatexchanger (24) and which is connected to user side heat exchangers (33)by means of an existing liquid side communication pipe (60) and anexisting gas side communication pipe (70); and a recovery container (40)which is provided on a suction side of the compressor (21) in the heatsource side circuit (11) and which traps refrigerating machine oilseparated from the gas refrigerant, the refrigerating apparatusperforming cleaning operation for recovering refrigerating machine oilfor the old refrigerant remaining in the existing liquid sidecommunication pipe (60) and the existing gas side communication pipe(70) to the recovery container (40) by operating the compressor (21),wherein the gas side communication pipe (70) which is connected to theheat source side circuit (11) of the refrigerant apparatus is composedof a plurality of branch pipes (71) respectively connected to theplurality of user side heat exchangers, and a stem pipe (72) to whichthe plurality of branch pipes (71) are connected, and an operationcondition in the cleaning operation is set based on a Froude number Frexpressed by an expression Fr=(d_(g)/d_(l))×(U²/gD) where U is avelocity of a gas refrigerant flowing through the stem pipe (72) of thegas side communication pipe (70), D is an inner diameter of the stempipe (72), d_(g) is a density of the gas refrigerant flowing through thestem pipe (72), d_(l) is a density of a liquid existing in the stem pipe(72), and g is a gravitational acceleration.
 5. The refrigeratingapparatus of any one of claims 1, 2, 3, and 4, wherein the operationcondition in the cleaning operation is set so that the Froude number islarger than
 1. 6. The refrigerating apparatus of any one of claims 1, 2,3, and 4, wherein the operation condition in the cleaning operation isset so that the Froude number is 1.5 or larger.
 7. The refrigeratingapparatus of any one of claims 1, 2, 3, and 4, wherein the refrigerantfilled in the heat source side circuit (11) is a mixed refrigerantcontaining R32 or a natural refrigerant.